autoplay block no longer conflicts with timeline change pause

fix brave/browser-laptop#8897

Auditors: @bridiver, @bbondy

patches/master_patch.patch

@@ -2004,10 +2004,38 @@ index df954bc8f81850101676b1c20f688ba0ba6b4b09..4683b2853bb467ec9f58616ede207d45
 
  // Non-standard APIs
 diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
-index b80b134d9db6ebee55af88010de2718ed46d1860..cd1a7d38170bc705f882ef824d24f070ca7c2255 100644
+index b80b134d9db6ebee55af88010de2718ed46d1860..eb50c91fb2d7235f70398345eabe712c349870ca 100644
 --- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
 +++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
-@@ -3905,6 +3905,10 @@ void HTMLMediaElement::unlockUserGesture() {
+@@ -459,6 +459,7 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName,
+ m_playingRemotely(false),
+ m_inOverlayFullscreenVideo(false),
+ m_mostlyFillingViewport(false),
++ m_hasPlayed(false),
+ m_audioTracks(this, AudioTrackList::create(*this)),
+ m_videoTracks(this, VideoTrackList::create(*this)),
+ m_textTracks(this, nullptr),
+@@ -2261,7 +2262,7 @@ Nullable<ExceptionCode> HTMLMediaElement::play() {
+ if (isGestureNeededForPlayback()) {
+ // If we're already playing, then this play would do nothing anyway.
+ // Call playInternal to handle scheduling the promise resolution.
+- if (!m_paused) {
++ if (!m_paused || m_hasPlayed) {
+ playInternal();
+ return nullptr;
+ }
+@@ -2337,6 +2338,10 @@ void HTMLMediaElement::playInternal() {
+
+ m_canAutoplay = false;
+
++ // MUON(darkdh): timeline change will trigger a pause which conflicts with
++ // autoplay check
++ m_hasPlayed = true;
++
+ setIgnorePreloadNone();
+ updatePlayState();
+ }
+@@ -3905,6 +3910,10 @@ void HTMLMediaElement::unlockUserGesture() {
  }
 
  bool HTMLMediaElement::isGestureNeededForPlayback() const {
@@ -2018,6 +2046,20 @@ index b80b134d9db6ebee55af88010de2718ed46d1860..cd1a7d38170bc705f882ef824d24f070
  if (!m_lockedPendingUserGesture)
  return false;
 
+diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.h b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+index a1e734c4bd78d1740da67938702aa71ea34b10a3..796b9d60e5224169404388816353425266be0c64 100644
+--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.h
++++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+@@ -667,6 +667,9 @@ class CORE_EXPORT HTMLMediaElement
+
+ bool m_mostlyFillingViewport : 1;
+
++ // MUON(darkdh): video has been played
++ bool m_hasPlayed;
++
+ TraceWrapperMember<AudioTrackList> m_audioTracks;
+ TraceWrapperMember<VideoTrackList> m_videoTracks;
+ TraceWrapperMember<TextTrackList> m_textTracks;
 diff --git a/third_party/WebKit/Source/web/WebArrayBuffer.cpp b/third_party/WebKit/Source/web/WebArrayBuffer.cpp
 index 271ec5391d8a9a478f36da58f1b539963cf39724..cd0fcf8bec875485097560c9c8231ad013cc0a96 100644
 --- a/third_party/WebKit/Source/web/WebArrayBuffer.cpp